Pumping system



March 12, 1963 L. H. BROWNE PUMPING SYSTEM 2 Sheets-Sheet 1 Filed Dec.19, 1958 FIG.

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ORNEYZ ATT March 12, 1963 1.. H. BROWNE PUMPING SYSTEM 2 Sheets-Sheet 2Filed Dec. 19, 1958 IN VEN TOR.

ATTORNEYS nit This invention relates to a pumping system and hasparticular reference to the pumping of materials, such as radioactivematerials, wherein the actual pumping must be elfected remote from thecontrol devices.

In my Patent No. 2,836,121, dated May 27, 1958, there is disclosed apump which has highly desirable characteristics of operation. in thesepumps, pulsators of rubber-like material serve as displacement elementsto effiect pumping in arrangements which serve for local isO- lation ofthe material being pumped from actuating liquid and the controlsproducing flows of the latter. Furthermore, desirably these pumpsprovide substantially continuous non-pulsating flow of the materialbeing pumped.

The isolation which is effected by the use of the pulsatons is, however,not sutlicient to satisfy the problems involved in the pumping, forexample, of dangerous radioactive materials. A solution to the latterproblem involves the arrangement of several pumping heads in tandemfashion with the utilization of liquid connections between them throughpiping serving for spatial isolation.

However, certain problems are not so simply solved since in the handlingof dangerously radioactive materials it would not be considered safe torely upon rubber or rubber-like diaphragrns or other pulsating elementsto form part of the system containing the dangerous materials. Thepractice in this respect is to utilize an all metal construction givingrise to a "very high safety factor against puncture or leakage, -alljoints being welded or otherwise made safely tight.

The utilization of metallic diaphragms, or the like, is attended with acharacteristic which give-s rise to special problems, namely, the factthat such diaphragms have a very considerable stiffness which must beovercome in effecting their movements in pumping operations. Inaccordance with the present invention, provisions are made to operatemetallic diaphragms, or other metallic displaceable walls such asbellows, in such fashion as to overcome their inherent stiffness While,nevertheless, utilizing the advantages of my pumping system in securingsubstantially uniform non-pulsating delivery.

The broad objects of the invention have to do with the attainment of thegeneral results just indicated, and these and other objects particularlyrelating to details of construction and operation will become apparentfrom the following description read in conjunction with the accompanyingdrawings, in which:

FIGURE 1 is a vertical section through a driving liquid distributingvalve and associated parts, the section being taken on the plane thetrace of which is indicated at 11 in FIGURE 2;

FIGURE 2 is a horizontal section taken through the same; and

FIGURE 3 is a diagrammatic sectional view showing actuating and pumpingheads associated with and adapted to be operated by the mechanism shownin FIGURES 1 :and 2.

There will first be described the primary pumping means which isdesirably utilized in the present system and which will be found tocorrespond very closely in many respects to what is described in myPatent No. 2,836,121.

The particular spatial arrangement of the various parts arm ice

of the primary pumping means is not of major consequence and,accordingly, various elements are indicated diagrammatically in ratherarbitrary location. A driv ing motor 2 serves to drive through shaftconnections indicated at 4 reduction gearing indicated as located withina housing 6 by which, in turn, there is driven a shaft 8 carryinga'crank 10 which through link 12 and pin 14 senves to reciprocate aslide 16 in a guideway 18 provided in a valve block 20. The variouselements so far described are desirably located within a pump housing aportion of the wall of which is indicated at 21, this housing alsoenclosing a primary pump 23 (FIGURE 2) which is driven by the motor 2.The pump 23 may be of any of a large variety of positive types. It hasbeen found, for example, that one highly satisfactory form of pump is ofmultiple piston, variable delivery type, which is capable of providingan output reasonably continuous and free from pulsation. -In such apump, for example, variation of displacement from zero to some maximumcapacity may be controlled by a manual adjusting device, though theadjustment of the pump may he automatically controlled eitherpneumatically or electrical y. Rotary piston or other types of positivevariable delivery pumps may also be used. The particular driving pumphere used does not, in itself, constitute a part of the invention, theinvention being concerned only with the use of a positive pump desirablyhaving substantially uniform displacement, and under some circumstances,desirably adjustable as to delivery rate. A constant rate pump may beused where adjustability is not required. Conveniently, the housingwhich encloses the elements described, including the pump, may providean oil sump from which oil may be pumped through the system withdelivery back to the sump. The oil used may be any suitable lubricatingoil and may serve not only as the driving liquid but also forlubrication of the mechanically operating parts.

A valve cylinder 26 is located with a press fit in a bore 24 in theblock 20, and arranged to reciprocate in cylinder 26 is a driving liquiddistributing valve generally designated 28. This valve comprises themain pistons 30 and 32 and end pistons 34 and 36. The spindle of thevalve is bored at its ends to receive rods 33 which are arranged to beengaged by discs 22 threaded on studs 25 secured in the ends of theslide 16, the discs being located in binding condition against the rods38 and held by lock nuts. The purpose of the arrangement just describedis to provide axial adjustability of the. valve 28 with respect to theslide 16 to provide for proper phasing of its respective operations ashereafter described. Through the connections from crank it) the valve isgiven approximately simple harmonic motion for control of the drivingliquid flow. A central port 40 is provided in block 20 and cylinder 26to serve for the introduction of operating liquid through pipe 41 fromthe pump 23.

Various ports are provided in axially displaced positions along thecylinder 26 and provide communication between its bore and annularspaces about the cylinder provided in the block 24). Each of these'portsdesirably consists of a number of radial holes through the cylinder, asindicatcd in FIGURE 1, to provide free flow of the driving liquid, butfor convenience will be hereafter referred to in the singular. 7

Ports 42 and 44 provide for delivery of the driving liquid from thecentral portion of the cylinder 26. These ports communicate with thespaces 46 and 48 in the block 29.

Ports 5G and 52 provide for the exhaust of driving liquid from pulsatorshereafter described and communicate with the spaces 54 and 56 in theblock 20.

Ports 58 and 60 provide for exhaust of the operating 3 liquid from thecylinder 26 and communicate with the spaces 62 and 64 in the block. Thespaces 62 and 64 are respectively ported at 66 and 68 to connectingpipes 67 and 69 which serve to return the exhausted driving liquid tothe sump.

As will appear hereafter, the valve pistons serve to control flowsthrough the various cylinder ports.

The spaces 54 and 56 are in communication with passages 7t and 72 in theblock 29. Spaces 46 and 48 communicatc with the openings through valveseats 7 8 and 80 which are, respectively, controlled by ball checkvalves 74 and 76 above which, as viewedin FIGURE 2', are locatedpassages 75 and 77 communicating, respectively, through lateral passages90 and 92 with the passages 70 and 72. Inwardly directed fins 93 guidethe balls and provide for passage of liquid 'by the balls. Springs 82and 84 serve to urge the balls 74 and 76 towardseated position, thesesprings being located within plugs 86 and 88 in the passages 75 and 77,the plugs being provided with packing to provide against leakage fromthese passages. Snap rings 79 and 81 hold the plugs 86 and 88 inposition. The bores 70 and 72 are in communication with bores 99 and 97,respectively, provided in a block 94 which is mounted on the wall 21 ofthe housing and serves to support, in an opening through this wall, theblock 20. Sealing between the block 20 and block 94 at the passages isprovided by O-rings as illustrated in FIGURE 2. Communicating with thebores 97 and 99 are pipes 96 and 98 extending to pulsators.

Consideration may now be given to FIGURE 3 which shows the elements ofthe pumping system beyond the pipes 96 and 98 and terminating with thepumping head handling the ultimate material to be pumped. In FIG- URE 3,the elements associated with pipe 96 are shown in detail, and it will beunderstood that identical elements are associated with pipe 98, therebeing at the right-hand end of this figure the ultimate valvesassociated with the particular pumping head associated with pipe 98.

A pulsator head generally designated '150 comprises a pair of housingmembers 152 and 154'providing between them a chamber 155 in which ismounted a diaphragm 156. This diaphragm may be of suitable metallicconstruction and may be welded at its periphery between and to themembers 152 and 154. It will be understood that the showing of thisdiaphragmis more, or less diagrammatic and that the diaphragm, desirablymetallic, may actually consist of a metallic bellows, or the like,providing a displaceable wall. Whatever its form, for the purposes forwhich the invention is primarily intended, it will ordinarily haveconsiderable stiffness. 96 communicates with the chamber 155 at 158 atthe lefthand side of the diaphragm 156.

The chamber 155 at the other side of the diaphragm comunicates throughopenings 160 with a bore 162 which communicates with the interior of 'astandpipe 164 desirably of enlarged horizontal cross-section which isprovided with a tubular extension 166 at its upper end which is arrangedto be sealed off, for example, by welding, after the system is filledwith liquids. The portion of chamber 155 to the right of diaphragm 156and the passages communicating therewith and the lower part of standpipe164 are desirably filled'with heavy liquid 168, such as mercury, whichas will appearis provided to impose a large static head at theright sideof diaphragm 156. The standpipe is provided withsufii cient volume sothat the liquid 168 which will hereafter be referred to as mercury willnot pass into tube 172 communicating with the upper end of thestandpipe,which tube 172 and the upper portion of thestandpipe are filled withlighterliquid 170 such as water.

The tube 172 may pass through a heat exchanger such as 174 which may beprovided, if required, for cooling purposes and thence-at 176communicates with a pumping head 189 which to a considerable extentinvolves the same construction as the actuating head 150 comprising Thepipe 7 housing members 182 and 184 providing between them a chamber 185within which is located a diaphragm 186 which may also be of stiffmetallic material. The pipe 176 communicates with the portion of thechamber 185 to the left of the diaphragm 186 at 188. The righthand sideof this chamber communicates through passages 190 with a bore 192 whichat its lower end communicates wtih a supply of the material being pumped(which may be a liquid, :1 liquid containing a suspended solid material,a vapor or gas) through one or more check valves indicated at 194. Atits upper end the *bore 192 communicates with a delivery line for thepumped material through one or more check valves 196. (The reason forindicating check valves in tandem is that in operations involvingdangerous materials it is usually desirable to insure against any faultyoperation by the use of check valves in series, though from thestandpoint of normal operation these are merely the equivalent of asingle check valve.)

While the elements communicating with pipe 98 are not detailed, it willbe understood that they are identical with those shown in FIGURE 3 asconnected with pipe 96, and there are shown at the right of FIGURE 3 thecheck valves 194' and 196' of the pumping head 18!) associated with pipe98. The lower check valves 194 and 194' communicate with a materialintake manifold 198 and the outlet check valve 196 and 196 communicatewith a delivery manifold 200.

The pipes 96 and 98 and 172 and that corresponding with the otherassembly which is not detailed may obviously be of any desired lengthserving to provide isolation such as may be required for the materialbeing pumped. Oil is desirably the liquid which flows through pipes 96and 98, while Water may be the liquid in pipe 172 and its counterpart.

If it were assumed that the diaphragms 156 and 186 involved nosubstantial stiffness, the system would operateeven in the absence ofthe mercury head to provide continuous non-pulsating delivery of thematerial being pumped through the manifold 200 for reasons set forthmore fully below. In such case, the effect would be essentially that ofthe diaphragms 156 and 186 being equiv-- alent to pulsators of the typedescribed in my prior patent, the liquid connections being merelytransfer connections for the displacements involved. The sum of thedisplacements of the diaphragms 186 of the two pumping heads. toward theright to efiect pumping would be constant, though the intakes of thematerial being pumped through the intake manifold 198 and the valves 194and 194" would be intermittent. These pumping conditions arenotdisturbed by the inclusion of the elements which have been shown anddescribed but they become necessary forthe following reasons:

The stiffness of the diaphragm 156, resisting its movement to an extremeleft-hand position as illustrated in FIGURE 3, might involve asubstantial pressure difference forming a large percentage ofatmospheric pressure or even exceeding that pressure. Then, in turn,even assuming some residual pressure difference, only this residualpressure difference would be available toovercome the stiffness of thediaphragm 186 and the possible suction required at the inlet for thematerial being pumped. Accordingly, there are provided the mercurycolumns which have been described. As the diaphragm 156 is forced to theright under the full pressure exerted by the pump 23, which may be veryhigh,

the mercury column is raised. Then when conditions for the collapse ofthe pulsator occurs, the mercury column exerts the necessary pressure todrive the diaphragm 156 to its left-hand position, leaving for thedriving of the diaphragm 186 essentially atmospheric pressure less onlythe vapor pressure of the water or other liquid in pipe 172. Thediaphragm 186 must, of course, be made such as to be properly movedtoward the left by the pressure gradient thus available. It will beevident that the foregoing considerations will not disturb thecondition, described below, of securing non-pulsating pumping action inthe heads 1% and 18d.

There may now be considered the matters which should be taken intoaccount to prevent damage and to secure proper operation despitetemperature changes. The liquid spaces between the right-hand side ofdiaphragm 156 and the left-hand side of diaphragm 186 should be chargedwith the liquids (for example, mercury and water) and sealed when thesystem is at its minimum temperature and with the diaphragms 156 and 186in their extreme lefthand positions, the extreme left-hand position ofdiaphragm 186 being desirably with some clearance with the left-handwall of the chamber 135. Thereafter, if the temperature rises in thesystem, the diaphragm 186 cannot under any conditions again come incontact with the left side of its housing nor can it come in contactwith the right side of its housing if the chamber 185 is of sufficientsize (desirably substantially in excess of that of chamber 155), sinceits movements ar limited by the maximum displacements imparted to it bythe displacement of diaphragm 156. Thus, the diaphragm 186 cannot besubject to hydraulic shock due to interrupted discharge by bottoming.The diaphragm 156, on the other hand, is intended to attain its extremeleft-hand position,

as illustrated in FIGURE 3, upon each suction stroke, but the force oncontact will be no greater than that im posed by the pressure exerted bythe mercury column, assuming a zero suction head or" the material beingpumped. it follows that the stroke of diaphragm 156 always starts fromprecisely the same extreme left-hand position in each pumping cycle. Itmay be remarked that any change in volume in the oil connections (pipes96 and 9%) will be relieved automatically when the distributor valve 23effects opening to atmosphere once per cycle.

The operation which provides smooth non-pulsating flow is as follows:

Preliminarily, it may be remarked that the rate of rotation of the shaft8 for the purpose of reciprocating the distributing valve 22% throughits cycles is such that, considering the maximum delivery of pump 23, itthe delivery rate of the pump is adjustable, the pulsators 156 and thatcorresponding thereto connected with the pipe 98 will not be displacedduring any cycle toward the right as viewed in FIGURE 3 to such extentas to cause them to engage the walls of their respective chambers.Variations in delivery rate of the pumping liquid by pump 23 then merelyinvolves less displacement of the pulsators to provide correspondingdisplacement of the liquid being pumped.

There may be first assumed the conditions involved when the valve 2%occupies its extreme left-hand position as viewed in PEGURE 2. Underthat condition, the port &2, is in communication with the supply port 40for the operating liquid which will then be flowing past valve 74 shownas open in FIGURE 2 and through passages 99, 7 (i and 9% to provideexpansion of the pulsator connected to pipe 98. As this flow continues,the pulsator reduces the volume in its pumping chamber providing outflowof the mercury. Outflow port 5t) is closed by piston 30-. The inlet port44 is closed by piston 32. Ports 52 and 6d are in communicationwith eachother through the space between the pistons 32 and 36 and are also incommunication with the outlet port 63. While check valve *76 is nowclosed, the interior of the pulsator connected thereto is in freecommunication with the outlet and this pulsator will be in collapsedcondition under its head of mercury.

As the valve 28 moves toward the right from its lefthand position, thepiston 3t) continues to close port 50 and will not then have started toclose the port 42. Port 44 remains closed by piston 32 but this pistonwill now have closed the port 52, cutting oil communication be tween theinterior of the corresponding pulsator and the discharge port 63.Actually, at this time the pulsator will have been fully collapsed, and,consequently, flow right.

through the port 52 will have ceased before. the piston closes thisport. Inasmuch as port 42 is still open for the passage of the operatingliquid, the other pulsator will continue to expand.

The next event is the location of the valve 2.3 in a positioncharacterized by the beginning of opening of port 44 to the operatingliquid. As this port 44 is cracked open, there would occur a tendencyfor flow to take place from the expanded pulsator to the collapsedpulsator. if such action occurred, there would be produced, in view ofthe high pressures involved, a transient shock due to the interchange ofliquid from one pulsator to the other. However, such transfer of theoperating liquid is prevented by the closure or check valve 74- underthe action of spring 82. This check valve may close because, even thoughport 42 is open to the operating liquid supply, the pressure exertedinwardly by the expanded pulsator exceeds the inward pressure exerted bythe collapsed pulsator. This condition continues in fact, as thepulsator expands due to the flow of operating liquid thereinto inasmuchas until it receives the full volume of operating liquid it will be lessexpanded than the previously expanded pulsator. Accordingly, theincoming operating liquid following the attainment of the conditionsjust escribed will flow only into the newly expanding pulsator. As thisexpands it displaces mercury into its corresponding column. Thecondition existing, therefore, is that for a short interval after theattainment of these conditions the previously expanded pulsator willremain essentially in its fully expanded condition.

As further displacement of the valve 28 occurs with cut-off of port 42,flow continues into the newly expanding pulsator through port 44 andpast check valve '76 with no flow (with the exception of possible slightleakage) through port 42 in either direction. If any slight leakageoccurs, it would be from the fully expanded pulsator past check valve74- and through the space between pistons 36 and 32 to the otherpulsator under a relatively small head due to difierent extents ofexpansion or" the pulsators. Such slight flow, however, will not produceany noticeable transient in the nature of shock. Port remains closed.

The piston 3t then starts to open the port 59. The previously fullyexpanded pulsator is thus brought into communication through passages 99and and the space between pistons 3th and 34 and port 58 with the outletpassages 66, 67. In the absence of piston '34, the sudden application ofpressure at the left of piston 36' would cause the valve 28 to receive asharp impulse toward the However, with piston 34 provided, there isinvolved equalization of pressures efiective on the valve 28 to avoidthe occurrence of a transient at this time. The expanded pulsator nowcollapses due to its column of mercury. At this time, port 44 remainsopen so that flow of operating liquid continues to expand the otherpulsator. v

The final movement of valve 28 involves no new operation, the collapsingpulsator being completely collapsed before this final condition isreached, while the expanding pulsator continues to receive operatingliquid through the port 44.

It will be evident that the return of the valve to the initial positionmentioned involves merely repetition of the phases of the cycle but withinverse respect to the two pulsators.

Despite the intermittent openings and closings of ports, it will benoted that the sum of the expanded displacements of the two pulsators iscontinuous. The continuous supply of operating liquid involves, inparticular, total displacements of the two pulsators, first one, thenpossibly both, and then the other in such fashion that the total of theexpanded displacements in the chambers 1'55 remain constant.

While the complete system disclosed is arranged to provide non-pulsatingpumping, it will be evident that various aspects of the invention arenot limited theretobut may be used in systems in which pulsation in theoutflow is permissible and wherein, for example, the fiow' of liquid inconnections such as 96 and 98 may be due to the expansions andcontractions of pulsating elements. merely arranged as in my Patent No.2,738,731, dated. March 20, 1956, wherein pulsating pumping is effected.possibly relieved only to some extent by the operation, of a pluralityof pulsators operated out of phase. In, such an arrangement, there wouldstill be much utility in providing the equivalent of the mercury columnarrangement where transfer of displacements was required. to be efiectedthrough inherently stiff diaphragms or theirequivalents.

What is claimed is:

1. A pumping system comprising a housing, a movable diaphragm havingsubstantial stififness, said housing coop crating with said diaphragm todefine a pair of chambersv on opposite sides of said diaphragm, meansfor supplying a pulsating fiow of liquid into and out of one of said.chambers, pumping means driven by liquid pressure, and a conduit filledwith liquid and providing communication. between the other said chamberand said pumping means, a portion of said conduit including a standpipeextending upwardly with respect to said diaphragm, the liquid in saidstandpipe exerting a static pressure head on said diaphragm and saidpumping means being driven by liquid pressure communicated theretothrough said conduit.

2. A pumping system comprising a housing, a movable diaphragm havingsubstantial stifiness, said housing coopcrating with said diaphragm todefine a pair of chambers on opposite sides of said diaphragm, means forsupplying pulsating flow of liquid into and out of one of said chambers,a conduit for liquid communicating with the other of said chambers, saidconduit including means providing a standpipe for the exertion of liquidpressure on said diaphragm, said conduit containing a pair of liquids ofsubstantially different specific gravities, the liquid of greaterspecific gravity being in contact with said diaphragm and having aninterface with the liquid of less specific gravity in said meansproviding a standpipe, and pumping means communicating with said otherchamber through said standpipe and driven by the liquid pressuretherein.

3. A pumping system according to claim 2 in which the liquid of greaterspecific gravity is mercury,

4. A pumping system in which there are two complete sets of the elementsspecified in claim 2 and in which the movable diaphragms substantiallyalternate in their movements.

5. A pumping system comprising a housing, a movable diaphragm havingsubstantial stillness, said housing cooperating with said diaphragm todefine a pair of chambers on opposite sides of said diaphragm, means forsupplying pulsating flow of liquid into and out of one of said chambers,a conduit for liquid communicating with the other of said chambers, saidconduit including means providing a standpipe for the exertion of liquidpressure on said diaphragm against the pressure exerted by saidpulsating flow, a second housing, a second movable dia phragmcooperating with said second housing to define a second pair of chamberson opposite sides of the second diaphragm, said conduit being connectedwith one of the last mentioned pair of chambers, and means providinginlet and outlet passages to and from the other of the last mentionedpair of chambers for fluid to be pumped.

6. A pumping system comprising a housing, a movable diaphragm havingsubstantial stiffness, said housing cooperating with said diaphragm todefine a pair of chambers on opposite sides of said diaphragm, means forsupplying pulsating flow of liquid into and out of one of said chambers,a conduit for liquid communicating with the other of said chambers, saidconduit including means providing a standpipe for the exertion of liquidpressure on said diaphragm, said conduit containing a pair of liquids ofsubstantially different specific gravities, the liquid of greaterspecific gravity being in contact with said diaphragm and having aninterface with the liquid of less specific gravity in said meansproviding a standpipe, a second housing, a second movable diaphragmcooperating with said second housing to define a second pair of chamberson opposite sides of the second diaphragm, said conduit being connectedwith one of the last mentioned pair of chambers, and means providinginlet and outlet passages to and from the other of the last mentionedpair of chambers for fluid to be pumped.

7. A pumping system according to claim 6 in which the liquid of greaterspecific gravity is mercury.

8. A pumping system in which there are two complete sets of the elementsspecified in claim 5, in which the first mentioned movable diaphragmssubstantially alternate in their movements, and in which said inletpassages are joined and in which said outlet passages are joined for thepumping of the same fluid.

'9. A pumping system in which there are two complete sets of theelements specified in claim 6, in which the first mentioned movablediaphragms substantially alternate in their movements, and in which saidinlet passages are joined and in which said outlet passages are joinedfor the pumping of the same fluid.

10. A pumping system according to claim 8 in which said means forsupplying pulsating flows of liquids to the first mentioned diaphragmscomprise valve means for controlling the pulsating flow to effectsubstantially constant total driving displacements of saidfirstmentioned diaphragms.

11. A pumping system according to claim 9 in which said means forsupplying pulsating flows of liquids to the first mentioned diaphragmscomprise valve means for controlling the pulsating flow to eitectsubstantially constant total driving displacements of saidfirst-mentioned diaphragms.

References fiitcd in the file of this patent UNITED STATES PATENTS1,101,266 Franklin June 23, 1914 2,452,526 Osborne Oct. 26, 19482,915,016 Weaver et al. Dec. 1, 1959 FOREIGN PATENTS 473,442 Italy July28, 1952 1,122,901 France Sept. 14, 1956

1. A PUMPING SYSTEM COMPRISING A HOUSING, A MOVABLE DIAPHRAGM HAVINGSUBSTANTIAL STIFFNESS, SAID HOUSING COOPERATING WITH SAID DIAPHRAGM TODEFINE A PAIR OF CHAMBERS ON OPPOSITE SIDES OF SAID DIAPHRAGM, MEANS FORSUPPLYING A PULSATING FLOW OF LIQUID INTO AND OUT OF ONE OF SAIDCHAMBERS, PUMPING MEANS DRIVEN BY LIQUID PRESSURE, AND A CONDUIT FILLEDWITH LIQUID AND PROVIDING COMMUNICATION BETWEEN THE OTHER SAID CHAMBERAND SAID PUMPING MEANS, A PORTION OF SAID CONDUIT INCLUDING A STANDPIPEEXTENDING UPWARDLY WITH RESPECT TO SAID DIAPHRAGM, THE LIQUID IN SAIDSTANDPIPE EXERTING A STATIC PRESSURE HEAD ON SAID DIAPHRAGM AND SAIDPUMPING MEANS BEING DRIVEN BY LIQUID PRESSURE COMMUNICATED THERETOTHROUGH SAID CONDUIT.